1. Regaining Muscle Strength & Endurance
Rehabilitation Techniques for sports medicine and athletic training: william e. prentice

2. introduction
Following musculoskeletal injury there will be some degree of impairment in muscular strength and endurance
Rehabilitation program must focus on regaining and improving strength and endurance
Through thorough evaluation; identify weak links and address them during rehabilitation program
Injured area and along kinetic chain

3. introduction
Muscle Strength: ability for muscle to generate force against some resistance
Weakness or imbalance can impair normal functional movement
Muscle Endurance: ability to perform muscle contractions against some resistance for an extended period of time
As strength increases there is a corresponding increase in endurance
When Developing rehab. Plan, you must have an understanding of what you are trying to accomplish

4. Types of skeletal muscle contraction
Isometric: muscle contracts to produce tension, but there is no change in muscle length
Considerable force can be generated even though no movement occurs
Concentric: Muscle shortens in length, while tension increases to overcome or move some resistance
Eccentric: Muscle lengthens while producing tension
Resistance is greater than the muscular force being produced

5. Types of skeletal muscle contraction
Recommended that strengthening programs include exercises that strengthen muscles in a manner in which they contract functionally
All muscles function concentrically, eccentrically, and isometrically in 3 planes of motion
Rehab plan may begin with single joint, single plane isolated contractions, but should progress to multi- plane, multi-joint functional movement

6. Factors that determine levels of muscular strength, endurance & Power
Size of muscle
Number of muscle fibers
Neuromuscular efficiency

7. Factors that determine levels of muscular strength, endurance & Power
Size of muscle
Muscular strength is proportional to the cross- sectional diameter (CSD) of muscle fibers
Greater the CSD, or bigger a particular muscle is, the stronger it is, thus more force it is capable of generating
Size of muscle can increase with resistance training
Hypertrophy: increase in muscle size
Atrophy: Decrease is muscle size

8. Factors that determine levels of muscular strength, endurance & Power
Number of muscle fibers
Strength also determined by the number of muscle fibers within a given muscle
Inherited characteristic
Person with a large # of muscle fibers has the potential to hypertrophy to a much greater degree than someone with relatively few fibers
Through resistance training we can increase size of muscle fibers, but NOT the number of muscle fibers within a given muscle

9. Factors that determine levels of muscular strength, endurance & Power
Neuromuscular Efficiency
Strength is also directly related to the efficiency of the neuromuscular system and the function of the motor unit in producing muscular force
Motor unit: motor nerve and group of muscle fibers it innervates
Electrical impulse from CNS through motor nerve to muscle fibers it innervates cause muscle contraction
Initial increases in strength during 1st 8 to 10 weeks of a resistance training program can be attributed primarily to increased neuromuscular efficiency
Increase in # of motor units being recruited
Firing rate of each motor unit
Synchronization of motor unit firing

10. Muscle Fiber and Motor Unit

11. Muscle Fiber and Motor Unit

12. Fast-Twitch vs. slow-twitch
All muscle fibers in a particular motor unit are either fast-twitch or slow-twitch
Each has distinctive metabolic and contractile capabilities
Slow twitch
Type I or slow oxidative fibers
First on and last off
Resistant to fatigue, however time required to generate force is greater
Associated primarily with long duration aerobic-type activities

13. Fast twitch vs. slow-twitch
Capable of producing quick, forceful contractions, but fatigue more rapidly than Type I
Useful in short term, high intensity activities which mainly involve anaerobic system
2 types
Type IIA or fast-oxidative-glycolytic
Second on Second off
Type IIB or fast-glycolytic
Last on and first off
Fatigue rapidly
“true” fast twitch fibers

14. Fast-twitch vs. slow-twitch
Ratio in muscle
Within a particular muscle there are Type I and II muscle fibers
Ratio of types varies with each person
Muscles whose primary function is posture against gravity tend to have more slow twitch
Muscles that produce powerful, rapid, explosive strength movements tend to have a higher percentage of fast-twitch

15. Fast-twitch vs. slow-twitch
Ratio in muscle continued
Genetically determined and may play a part in determining ability for given sport activity
Must recognize what muscle fibers you are targeting during your rehabilitation plan and develop appropriate exercises
Can improve metabolic capabilities of each type through specific strength and endurance training
Can change Type IIB to Type IIA, but cannot change type II to Type I or vice versa

16. Physiology of Strength Development
Muscle Hypertrophy
Increase in size of muscle fiber
Theorized that dormant capillaries might become filled with blood to meet demands of increased blood flow from resistance training
Theorized that there is an increase in size and number of actin and myosin (myofilaments) within the muscle fiber
Thus muscle fibers increase in CSD
Hyperplasia: Increase in # of muscle fibers
Seen only in animal studies and not generalized for humans

17. Physiology of Strength Development
Reversibility
If resistance training is discontinued or interrupted, muscle will atrophy, decreasing strength and mass
As little as 48 hours
Consistent resistance training is essential to maintain strength and size

18. Techniques of Resistance Training
Overload Principle
For a muscle to improve strength it must be forced to work at a higher level than it is accustomed to.
Must be overloaded
Without overload, strength can be maintained with low to moderate intensity resistance training, but will not increase
Might be good training method for muscular endurance
In rehabilitation, progression may be limited by tissue healing and athletes pain, however most injuries will result in atrophy or be caused by atrophy of one or multiple muscles, so hypertrophy will lilely be goal of rehab. plan

19. Techniques of Resistance Training
SAID Principle
Specific Adaptations to Imposed Demands
When body is subjected to stress and overloads of varying intensities, it will gradually adapt over time, to overcome demands placed on it
Must apply term to different phases of rehab.
What are you trying to accomplish? BE SPECIFIC
For example: When reconditioning a basketball player would you want to have them run a mile?

20. Techniques of Resistance Training
Isometric Exercise
Used in early phases of rehabilitation when full ROM exercises exacerbate symptoms or could cause further injury
10 second hold for 10+ repetitions per hour recommended
Can be useful in strength increases at specific point in ROM
Submaximal to maximal intensities
Must be careful with increase in intrathoracic pressure (Val Salva) that occurs with maximal contractions
Also used by weight lifters to help increase strength at “sticking point” during a specific lift

21. Techniques of Resistance Training
Progressive Resistive Exercises(PRE)
Exercises that strengthen muscles through a contraction that overcomes some fixed resistance
Dumbbells, machines, elastic tubing
Uses isotonic contractions: contractions in which force is generated while muscle is changing length
Concentric and eccentric contractions

22. Concentric vs. Eccentric
Can generate more force against resistance with an eccentric contraction
Movement requires lower level of motor unit activity to achieve certain force than a concentric contraction
With fewer motor units firing to produce specific force additional motor units can be recruited to generate increased force
Eccentric contractions are less resistant to fatigue because requirement for Oxygen is less

23. Concentric vs. Eccentric
Eccentric contractions during rehabilitation have recently received considerable emphasis in research
Eccentric contractions critical in deceleration of limb motion, especially during high velocity dynamic activities
Strength deficits or inability to tolerate these forces may predispose a person to injury
Should focus on concentric and eccentric exercises during rehabilitation
Concentric movement: 1-2 seconds
Eccentric contraction: 2-4 seconds
Ratio of concentric to eccentric should be approximately 1:2
Muscle will fatigue more rapidly concentrically than eccentrically
Eccentric loading can assist in increasing tensile strength of healing tissue

24. Progressive Resistive Exercises(PRE)
Repetitions: number of times a specific movement is repeated
Repetition Maximum: Maximum # of repetitions at a given weight
Set: A group of repetitions and recovery intervals
Intensity: Amount of weight or resistance lifted
Recovery Period: rest interval between repetitions and sets
Volume: Amount of work (reps x sets) in a given training session
Frequency: # of training sessions in a week’s period
Periodization: preplanned, systematic variations in training specificity, intensity and volume organized in periods or cycles
Used in strength and conditioning, but should also be used in rehabilitative setting

25. Periodization Model for Resistance Training

26. Free weights vs. Exercise machines
Can be safer and easier to use
Design constraints often only allow single plane motions
Not very functional
Free weights
Element of neuromuscular control to stabilize weight from moving in different directions
May decrease amount of weight lifted compared to machine
Machines have restricted motion
Can incorporate multi-joint, multi-plane functional movements

27. Surgical tubing/theraband
Widely used in rehabilitation
Can perform isolated strengthening exercises or multi joint, multi-plane exercises
Easy for athlete to use at home
Can purchase different resistance levels identified by colors
Athlete can adjust resistance by increasing or decreasing tension on the band
Movement can occur in multi planes simultaneously
Exercise against resistance in more functional movement planes

28. Plyometric Exercise Incorporated in later stages of rehabilitation
Hops, bounds, depth jumps, weighted throws and rotations
Specific exercises that require a rapid stretch of a muscle eccentrically followed immediately by a rapid concentric contraction
Increase ability to use stored elastic energy
Affected by time, magnitude of stretch and velocity of stretch
Facilitate and develop a forceful, explosive movement over a short period of time
Help in developing eccentric control in dynamic movements

29. Open vs. Closed Kinetic Chain exercises
Open chain: foot or hand is not in contact with ground or some other surface
Closed Chain: Foot or hand is weight bearing or fixed on ground or surface
Most functional activities involve some aspect of weight bearing for the feet or hands
May start with open chain exercises, but must progress to closed chain exercises to optimize rehabilitation
Closed chain exercises will transmit forces throughout kinetic chain
Strengthening and stabilization of multiple muscles and joints

30. Conclusion
During rehabilitation must incorporate muscle strength and endurance exercises
Assist in tissue healing by realignment of scar tissue and increasing tensile strength
Identify weaknesses and address during rehab program
Strength deficits or atrophy from the injury or that may have predisposed athlete to the injury
Use progressive resistance exercises following periodization, overload and specificity principles when developing rehab program
Communication with the athlete is essential to proper progression of resistive exercises
Pain and swelling can help guide your progression